Historically,
American Airlines,
Continental Airlines (acquired by United), and
Northwest Airlines (acquired by Delta) offered lifetime lounge memberships.
While I happen to hold all three, many FlyerTalkers hold one or two. All offer both similar and different products (AA=no partners unless on AA, not much F&B, but amazing showers, DL=no partners, better F&B, occasional showers, and UA=amazing partners + middle F&B and essentially no showers).
As of June 2019 Delta has announced that only LT Club members will have access when not on Delta+Partners;
UA and
AA followed the same but currently intend to exclude all customers, including lifetime, traveling on other airlines effective 11/1/19.
While I personally feel that ethical lounge operators should not charge for memberships unless accessible when flying regardless of airline, changing this benefit for lifetime members seems particularly egregious. I'm fine with airlines choosing not to sell lounge memberships, or adding conditions to people who have not yet joined (or for members past their current term), or just providing free/paid access to elite members while flying...but feel that changing terms post-sale is unethical.
Mods: while individual threads exist on airline pages, I feel this is a broader topic which should be discussed on this forum. For me this is an ethical question...after all if they'll take x away without compensation why no z? How would you feel about paying to fly F and getting NRSA privileges?